Intermediate Transfer Rates and Solid-State Ion Exchange are Key Factors Determining the Bifunctionality of In2O3/HZSM-5 Tandem CO2 Hydrogenation Catalyst.

Identifying the descriptors for the synergistic catalytic activity of bifunctional oxide-zeolite catalysts constitutes a formidable challenge in realizing the potential of tandem hydrogenation of CO2 to hydrocarbons (HC) for sustainable fuel production. Herein, we combined CH3OH synthesis from CO2 and H2 on In2O3 and methanol-to-hydrocarbons (MTH) conversion on HZSM-5 and discerned the descriptors by leveraging the distance-dependent reactivity of bifunctional In2O3 and HZSM-5 admixtures. We modulated the distance between redox sites of In2O3 and acid sites of HZSM-5 from milliscale (∼10 mm) to microscale (∼300 µm) and observed a 3-fold increase in space-time yield of HC and CH3OH (7.5 × 10-5 molC gcat-1 min-1 and 2.5 × 10-5 molC gcat-1 min-1, respectively), due to a 10-fold increased rate of CH3OH advection (1.43 and 0.143 s-1 at microscale and milliscale, respectively) from redox to acid sites. Intriguingly, despite the potential of a three-order-of-magnitude enhanced CH3OH transfer at a nanoscale distance (∼300 nm), the sole product formed was CH4. Our reactivity data combined with Raman, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) revealed the occurrence of solid-state-ion-exchange (SSIE) between acid sites and Inδ+ ions, likely forming In2O moieties, inhibiting C-C coupling and promoting CH4 formation through CH3OH hydrodeoxygenation (HDO). Density functional theory (DFT) calculations further revealed that CH3OH adsorption on the In2O moiety with preadsorbed and dissociated H2 forming an H-In-OH-In moiety is the likely reaction mechanism, with the kinetically relevant step appearing to be the hydrogenation of the methyl species. Overall, our study revealed that efficient CH3OH transfer and prevention of ion exchange are the key descriptors in achieving catalytic synergy in bifunctional In2O3/HZSM-5 systems.

Bronchodilator reversibility testing in morbidly obese non-smokers: a comparative study- few concerns.

This is a letter in response to an article by Ahmed et al., which concluded that in comparison to salbutamol, Fluticasone/salmeterol combination increases FEV1, FEV1% of predicted, and FEV1/FVC ratio, however it did not offer novel insights, as both agents met the 12%- and 200-mL reversibility benchmarks and Concerns about incorporating a combination medication that includes an inhaled corticosteroid, inhaled corticosteroids are not typically associated with bronchodilation.

Challenges and Opportunities for Exploiting the Role of Zeolite Confinements for the Selective Hydrogenation of Acetylene.

Zeolites, with their ordered crystalline porous structure, provide a unique opportunity to confine metal catalysts, whether single atoms (e.g., transition metal ions (TMIs)) or metal clusters, when used as a catalyst support. The confined environment has been shown to provide rate and selectivity enhancement across a variety of reactions via both steric and electronic effects, such as size exclusion and transition state stabilization. In this review, we provide a survey of various zeolite confined catalysts used for the semihydrogenation of acetylene highlighting their performance, defined by ethylene selectivity at full acetylene conversion, in relationship to the synthesis technique employed. Synthesis methods that ensure confinement with the catalyst transition metal location in the extra-framework positions are reported to have the highest selectivity to ethylene. However, the underlying molecular factors responsible for selective catalysis within confinement remain elusive due to the difficulty in deconvoluting individual effects. Through the careful use of a combination of characterization and spectroscopic methods, insights into the relationship between the properties of zeolite confined catalysts and their performance have been explored in other works for a variety of reactions. More specifically, operando spectroscopy studies have revealed the dynamic behavior of zeolite confined catalysts under various conditions implying that the structure and properties observed ex situ do not always match those of the active catalyst under reaction conditions. Applying this type of analysis to acetylene semihydrogenation, a simple gas phase reaction, can help elucidate the structure-function relationship of zeolite confined catalysts allowing for more informed design choices and consequently their application to a wider variety of more complex reactions such as the liquid phase hydrogenation of alkynols where solvent effects must also be considered in addition to those of confinement.

A Machine Learning Understanding of Sepsis.

Sepsis is a serious cause of morbidity and mortality and yet its pathophysiology remains elusive. Recently, medical and technological advances have helped redefine the criteria for sepsis incidence, which is otherwise poorly understood. With the recording of clinical parameters and outcomes of patients, enabling technologies, such as machine learning, open avenues for early prognostic systems for sepsis. In this work, we propose a two-phase approach towards prognostic scoring by predicting two outcomes in sepsis patients - Sepsis Severity and Comorbidity Severity. We train and evaluate multiple machine learning models on a dataset of 80 parameters collected from 800 patients at Amrita Institute of Medical Sciences, Kerala, India. We present an analysis of these results and harmonize consistencies and/or contradictions between elements of human knowledge and that of the model, using local interpretable model-agnostic explanations and other methods.

Directing the Rate-Enhancement for Hydronium Ion Catalyzed Dehydration via Organization of Alkanols in Nanoscopic Confinements.

Alkanol dehydration rates catalyzed by hydronium ions are enhanced by the dimensions of steric confinements of zeolite pores as well as by intraporous intermolecular interactions with other alkanols. The higher rates with zeolite MFI having pores smaller than those of zeolite BEA for dehydration of secondary alkanols, 3-heptanol and 2-methyl-3-hexanol, is caused by the lower activation enthalpy in the tighter confinements of MFI that offsets a less positive activation entropy. The higher activity in BEA than in MFI for dehydration of a tertiary alkanol, 2-methyl-2-hexanol, is primarily attributed to the reduction of the activation enthalpy by stabilizing intraporous interactions of the Cß -H transition state with surrounding alcohol molecules. Overall, we show that the positive impact of zeolite confinements results from the stabilization of transition state provided by the confinement and intermolecular interaction of alkanols with the transition state, which is impacted by both the size of confinements and the structure of alkanols in the E1 pathway of dehydration.

Transition-Metal Nitroprussides Examined for Water Harvesting and Sorption Cooling.

Transition-metal pentacyanonitrosylferrates, commonly known as nitroprussides, have a long and documented history. Here, we synthesize cobalt and nickel nitroprussides (NPs) in order to probe their use as sorbents for water and fluorocarbon uptake for potential water harvesting and cooling applications. These NPs show stable and reversible equilibrium sorption isotherms at room temperature with peak uptake values of ∼40 wt % for H2O and ∼30 wt % for fluorocarbon R134a. At water harvesting conditions, working capacities of ∼19 wt % were obtained for NPs. At sorption cooling conditions, the working capacities favored nickel NP. Given the advantages of an easy, inexpensive, and scalable synthesis, this study demonstrates the potential for using nitroprussides for future water harvesting and adsorption cooling systems.

Molecular Insight into Fluorocarbon Adsorption in Pore Expanded Metal-Organic Framework Analogs.

The rapid growth in the global energy demand for space cooling requires the development of more efficient environmental chillers for which adsorption-based cooling systems can be utilized. Here, in this contribution, we explore sorbents for chiller use via a pore-engineering concept to construct analogs of the 1-dimensional pore metal-organic framework MOF-74 by using elongated organic linkers and stereochemistry control. The prepared pore-engineered MOFs show remarkable equilibrium adsorption of the selected fluorocarbon refrigerant that is translated to a modeled adsorption-based refrigeration cycle. To probe molecular level interactions at the origin of these unique adsorption properties for this series of Ni-MOFs, we combined in situ synchrotron X-ray powder diffraction, neutron powder diffraction, X-ray absorption spectroscopy, calorimetry, Fourier transform infrared techniques, and molecular simulations. Our results reveal the coordination of fluorine (of CH2F in R134a) to the nickel(II) open metal centers at low pressures for each Ni-MOF analog and provide insight into the pore filling mechanism for the full range of the adsorption isotherms. The newly designed Ni-TPM demonstrates exceptional R134a adsorption uptake compared to its parent microporous Ni-MOF-74 due to larger engineered pore size/volume. The application of this adsorption performance toward established chiller conditions yields a working capacity increase for Ni-TPM of about 400% from that of Ni-MOF-74, which combined with kinetics directly correlates to both a higher coefficient of performance and a higher average cooling capacity generated in a modeled chiller.

Catalytic resonance theory: parallel reaction pathway control.

Catalytic enhancement of chemical reactions via heterogeneous materials occurs through stabilization of transition states at designed active sites, but dramatically greater rate acceleration on that same active site can be achieved when the surface intermediates oscillate in binding energy. The applied oscillation amplitude and frequency can accelerate reactions orders of magnitude above the catalytic rates of static systems, provided the active site dynamics are tuned to the natural frequencies of the surface chemistry. In this work, differences in the characteristics of parallel reactions are exploited via selective application of active site dynamics (0 < ΔU < 1.0 eV amplitude, 10-6 < f < 104 Hz frequency) to control the extent of competing reactions occurring on the shared catalytic surface. Simulation of multiple parallel reaction systems with broad range of variation in chemical parameters revealed that parallel chemistries are highly tunable in selectivity between either pure product, even when specific products are not selectively produced under static conditions. Two mechanisms leading to dynamic selectivity control were identified: (i) surface thermodynamic control of one product species under strong binding conditions, or (ii) catalytic resonance of the kinetics of one reaction over the other. These dynamic parallel pathway control strategies applied to a host of simulated chemical conditions indicate significant potential for improving the catalytic performance of many important industrial chemical reactions beyond their existing static performance.

Cooperative Co0 /CoII Sites Stabilized by a Perovskite Matrix Enable Selective C-O and C-C bond Hydrogenolysis of Oxygenated Arenes.

Strontium-substituted lanthanum cobaltite (La0.8 Sr0.2 CoO3 ) matrix-stabilized Co0 /CoII catalytic sites were prepared, which present tunable C-O and C-C hydrogenolysis activity for the vapor-phase upgrading of oxygenated arenes. CoII sites associated with oxygen vacancies were favored at low temperatures and performed selective C-O hydrogenolysis, in which Sr-substitution facilitated oxygen vacancy formation, leading to approximately 10 times higher reactivity compared to undoped LaCoO3 . Co0 sites were favored at high temperatures and performed extensive C-C bond hydrogenolysis, generating a wide range of alkanes. The lower reaction order with P H 2 (1.1±0.1) for C-C hydrogenolysis than for C-O hydrogenolysis (2.0±0.1) led to a high selectivity towards C-C hydrogenolysis at low P H 2 . The Co3 O4 surfaces featured a narrower temperature window for obtaining the respective optimal CoII and Co0 pairs compared to analogous perovskite surfaces; whereas, the perovskite matrix stabilizes these pairs for selective C-O and C-C hydrogenolysis. This stabilization effect offers an additional handle to control reactivity in oxide catalysts.